.btn(@width,@height,@font-size,@color:inherit,@bg:inherit){
  width: @width;
  height: @height;
  text-align: center;
  line-height: @height;
  font-size: @font-size;
  color: @color;
  background: @bg;
  //border:.border(@border-color,@border-width,@border-style);
}